Ultrashort wave modulated carrier wave radio communication system



March 16, 1937. v sE 2,073,643

'ULTRASHORT WAVE MODULATED CARRIER WAVE RADIO COMMUNICATION SYSTEM Original Filed Jan. 15, 1954 2 Sheets-Sheet 1 1 3g. 1. l ke. 2.

M M i INVEN'IO'R ALFRED A. LINSELL ATTORNEY March 16, 1937. A. A. LINSELL 2,073,643 ULTRASHORT WAVE MODULATED CARRIER WAVE RADIO COMMUNICATION SYSTEM 2 Sheets-Sheet 2 Original Filed Jan. 15, 1934 INVE N'T'OT ALFRED A. LINSELL ATTORNEY Patented Mar. 16, 1937 ULTRASHORT .WAVE MODULATED' OAR- RIER WAVE RADIO COMMUNICATION SYSTEM Alfred Aubyn Linsell, London, England, assignor to Radio Corporation of America, a corporation of Delaware Original application January 13, 1934, Serial No.

706,516. Divided and this application December 31, 1935, Serial No. 56,851

8 Claims.

This invention relates to ultrashort wave modulated carrier wave radio communication systems, and more particularly to modulated carrier Wave radio systems wherein the wave length employed is in the range sometimes referred to as the "quasi-optical range--i. e. centimeter waves, for example, waves of the order of 60 cm.

This application is a division of my copending application, entitled "Ultrashort wave modulated carrier wave radio communication systems, Serial No. 706,516, filed January 13, 1934 and as signed to the same assignee as the present application. Considerable diificulty is experienced in practice in modulating such ultrashort waves in a satisfactorymanner; for example, in the usual methods of applying modulation, e. g. in the method of anode modulation, undesired changes in frequency are occasioned by the application of the modulating potentials.

The invention has for its primary object to provide a simple and reliable system wherein gen eration and transmission of very high frequency waves and alsomodulation of the said high frequency waves can be satisfactorily effected, substantially withoutaffecting the oscillation generating or driving means. According to this invention, an ultrashort wave modulated carrier wave radio transmitting system comprises the combination of means for generating and radiating ultrashort waves, one or more conductors interposed in the path of the radiated waves and means for varying the impedance of said conductor or conductors in ac: cordance with modulating frequencies whereby the effect of said conductor or conductorsupon the radiated waves is varied.

It is well known that if a conductive obstacle be placedin the path of ultrashort waves, e, g; waves of the order of 60 c'm.or less, theradiation propriately tuned relative to the working wave length and, therefore, in carrying out the p-resent invention it is proposed to place a conductor. whose overall length may be equal tothat of an ultrashort wave radiator, in the path of the radiation therefrom, said conductor'consisting of a plurality of conductor portions connected in series with one another by the anode-cathode space or spaces of a valve or valves whose internal ime pedance or impedances is or are controlled in potential by and/orin accordance with modulating potentials. 'If the bias applied to the grid or grids of the valve or valves is suitably chosen, it is possible so to arrange matters that the conlili ductor as a whole, 1. e., including the anode-cathode space or spaces of the valve or valves, is made substantially conductive throughout its whole length during half cycles of modulation while during the other half cycles it will be equivalent to two or more sub-lengths (changing progressively from one state to the other in dependence upon the low frequency modulation) and since these sub-lengths do not bear any direct relationship to the high frequency waves being transmitted, they will not affect the radiation to the same extent as will occur when the conductor is substantially conductive over its whole length. As a result the outgoing waves will be modulated.

Preferably means are provided for preventing neutralizing shunting effect of the modulating wave or valves at the very high frequencies concerned by reason of the internal'self or interelectrode capacity thereof.

Preferably also the auxiliary conductor or conductors, i. e. the conductor or conductors by means of which modulation is effected, is or are located at a distance exceeding one wave length from the radiator whose emission is to be modulated.

In carrying the invention into practice, inductances of such value as to constitute chokes at the working frequency should be placed in the high tension supply leads and filament leads of the valve or valves so as to confine the high frequency to the anode-cathode path through the said valve or valves.

The invention is illustrated in and further explained in connection with the accompanying drawings, Figures 1 to 7 of which show various embodiments of the invention.

Referring to Figure 1 which shows, diagrammatically, one embodiment of the invention, there is provided an ultrahigh frequency radiator consisting of a dipole I, l having a suitable ultrahigh frequency oscillation generating arrangement 2 connected to energize it centrally. At a distance from this radiator exceeding one wave length, is an auxiliary conductor 3, 3, consisting of two conductive rods or wires connected together by the anode-cathode space of a thermionic valve 4. The auxiliary conductor is thus, as it were a dipole with the anode-cathode space of the valve 4 arranged between the halves thereof, although it is not necessary that the two parts between which the valve is interposed be equal. The auxiliary conductor arrangement 3, 3, 4, is parallel to the radiator arrangement I, |,'2. Low frequency modulating potentials are applied through a radio frequency choke Ch between the control grid and cathode of the valve 4 and the initial bias thereon is so adjusted that for one low frequency half cycle the anode-cathode path is made more conductive and for the other low frequency half cycle this path is made less conductive. Suitable steady potential is applied to the anode of the valve and the modulating potentials are applied to the grid thereof, for example, as indicated via a transformer T whose primary is connected to a microphone M (assuming speech modulation). For the sake of simplicity in the drawings, the sources of anode and grid bias potentials are omitted from Figure 1.

Preferably the shunting effect of the valve 4 at high frequency is neutralizedfor example as shown in Figure 2-by connecting between the anode and cathode of the valve 4 a non-radiating line 8 in series with a blocking condenser 9, the length of the line being such that any shunting effect at the high frequency and due to the valve capacity is neutralized. In Figure 2 the line 8 is caused to be substantially non-radiating by being bent back and forth upon itself.

In a further embodiment illustrated in Figure 3 the auxiliary conductor by which modulation is effected is divided into three portions connected in series by means of valves, there being thus two such valves and 6. Each valve has its own grid transformer T1 or T2 the primaries of thesetransformers being connected for energization from a microphone M or other source of modulating potentials in any convenient way, e. g. in series therewith.

It is not necessary that the auxiliary conductor be simply of straight rod-like construction. For example, the above described embodiments may be modified by arranging the valve or valves to connect in series conductive portions consisting each of a plurality of rod-like members in parallel, e. g. as shown in Figure 4, which may be regarded as a variation of the arrangement of Figure 1, there may be three parallel rod-like members 3a, 3b, 30 connected to the anode of each valve and three similar parallel members, similarly designated connected to the cathode thereof. Of course, any desired suitable arrangement of conductive portions may be employed, the essential requirements being merely that the modulating potentials shall vary the effect of the whole conductor arrangement (whatever it may be) upon the transmitted waves.

In yet a further embodiment illustrated in Figure 5 two (or more) auxiliary conductors each consisting of two or more portions 3, 3, or 3, 3 connected together in series through a valve or valves 4 or 4' are provided, these auxiliary conductors being all in the path of the waves from the radiator l, i, but at different distances from said radiator. These auxiliary conductors which each include one or more valves 4 or 4 and are similar to one another, may be of the same length as the radiator length, and should be parallel thereto. Modulating potentials are applied to the valves of all the auxiliary conductors in suitable phase relationship, e. g. if the distance between two adjacent conductors is an even number of half wave lengths, the modulating potentials should be applied to the valves in said conductors in phase, but if the distance between said conductors is an odd plurality of half wave lengths, the modulating potentials applied to the valves in one conductor should be 180 out of phase with the modulating potentials applied to the valves in the next.

In another method illustrated in Figure 6 of applying modulating potentials to a valve included in an auxiliary conductor employed in carrying out this invention, the modulating potentials are applied from M between grid and cathode of a low frequency v amplifying valve l0 whose plate circuit includes the primary of a transformer II in series with a pair of high frequency chokes l2, [3, connected one on each side of said primary. The secondary of this transformer, may be shunted by a high frequency bypass condenser l6 and is connected in series with the anode of-the modulating valve 4 between said anode and the portion of rod-like conductor which, in the previously described embodiments was directly connected to said anode. Anode potential is applied to the modulating valve 4 from a source HTl via the secondary of the transformer and a suitable high frequency choke M in series, the negative terminal of the anode battery being connected to the common cathode point of the two valves Ill and 4 to which point the negative terminal of the anode battery HTz for the amplifying valve and the positive terminal of a negative grid bias battery GB for the modulating valve 4 are also connected.

In a modification-illustrated in Figure '7-of the last described embodiment the transformer coupling arrangement for the audio frequency valve I0 is replaced by a choke coupling arrangement. The anode of the audio frequency valve l 0 is connected to the anode of the modulating valve 4 through a high frequency choke I1 and a low frequency choke 15 which may be shunted by a high frequency by-pass condenser I6 is connected in the position occupied in the last described embodiment by the secondary of the transformer. Thus both valves receive anode potential from a common source HT'1.

I claim:

1. An ultrashort modulated carrier wave radio transmitting system comprising a transmitting aerial, means for energizing said aerial with unmodulated energy at an ultrashort wave length whereby said aerial radiates said energy, an auX- iliary conductor interposed in the path of the energy radiated from said aerial, said auxiliary conductor comprising two conductive portions connected together by a thermionic'valve, and means for varying the internal impedance of said valve in dependence upon modulating potentials, and means for preventing shunting effects due to the self capacities of said valve electrodes.

2. In a device of the character of claim 1 further characterized in that said aerial and auxiliary conductors are. dipoles.

3. An ultrashort modulated carrier wave radio transmitting system comprising a transmitting aerial, means for energizing said aerial with unmodulated energy at an ultrashort wave length whereby said aerial radiates said energy, an auxiliary conductor interposed in the path of the energy radiated from said aerial, said auxiliary conductor comprising two conductive portions connected together by a thermionic valve, and means for varying the internal impedance. of said valve in dependence upon modulating potentials, and a non-radiating conductor and capacity connected across said valve to neutralize the capacities of said valve electrodes thereby preventing the shunting effects of said valve capacities.

4. In a device of the character described in combination, a transmitting aerial, a plurality of auxiliary conductors located at different distances from said transmitting aerial, thermionic valves having variable internal impedance effectively included in said conductors, means being provided for varying the internal impedances of the thermionic valves included in said conductors, and means for establishing such phase relationship with respect to the variable impedances of said thermionic valves as to cause said conductors to produce effects of like sense upon the energy radiated from the transmitting aerial. 5. In a device of the character described by claim 4, means for neutralizing the self-capacities of said thermionic valve electrodes to prevent the shunting efiect of said self-capacities.

6. An ultrashort modulated carrier wave radio transmitting system comprising a transmitting aerial, means for energizing said aerial with unmodulated energy at an ultrashort wave length whereby said aerial radiates said energy, and an auxiliary conductor interposed in the path of the energy radiated from said aerial, said auxiliary conductor comprising two conductive portions connected together by a thermionic valve having at least anode and cathode electrodes, and means for varying the internal impedance of said valve in dependence upon modulating potentials impressed between said anode and cathode electrodes.

7. In a device of the character of claim 6 means for neutralizing the shunting efiect caused by the effective self-capacities of said anode and cathode electrodes.

8. An ultrashort modulated carrier wave radio transmitting system comprising a transmitting aerial, means for energizing said aerial with unmodulated energy at an ultra short wave length whereby said aerial radiates said energy, an auxiliary conductor interposed in the path of the energy radiated from said aerial, said conductor comprising two conductive portions, a thermionic valve having an anode, cathode, and a control electrode and self-capacities between said elec- 

